World's Smallest Membrane Could Have Major Repercussions for Energy Industry

Researchers have created a membrane that, at 2 nanometers thick, is not only one of the world's thinnest, but is also highly selective.

The discovery could have widespread applications to the energy industry, the study's authors note.

Made from graphene oxide, the membrane allows hydrogen and helium to pass through, but puts up a fight against carbon dioxide, oxygen, nitrogen, carbon monoxide and methane, all of which permeate much more slowly.

The reason has to do with the size of the molecules..

"The membrane behaves like a sieve. Bigger molecules cannot go through, but smaller molecules can," Miao Yu, a chemical engineer from the University of South Carolina and the team lead, said in a statement.

The membrane was created by depositing flakes of graphene oxide on the surface of a porous aluminum oxide support, creating a circular membrane with an area of roughly 2 square centimeters.

The result is something of a mosaic, the researchers explain, likening it to a table covered in playing cards.

Because leaks between or within flakes are hard to avoid when working on such a small scale, microporous membranes designed to discriminate between molecules like this one are often much thicker, measuring around 20 nanometers.

By dispersing graphene oxide flakes in water and using sonication and centrifugation methods to create a semiliquid mixture, the researchers were able to achieve a thinner design.

The separation of carbon dioxide from other gases could have significant repercussions in the energy industry, the researchers note. Furthermore, they posit that the membrane could one day be used to purify water tainted by hydraulic fracturing (fracking).

"Having membranes so thin is a big advantage in separation technology," Yu said. "It represents a completely new type of membrane in the separation sciences."